Page 276 - Clinical Anatomy

ECA5 7/18/06 6:50 PM Page 261

The surface anatomy of the neck

In the midline, from above down, can be felt (Fig. 186):
1◊◊the hyoid bone—at the level of C3;
2◊◊the notch of the thyroid cartilage—at the level of C4;
3◊◊the cricothyroid ligament—important in cricothyroid puncture;
4◊◊the cricoid cartilage—terminating in the trachea at C6;
5◊◊the rings of the trachea, over the second and third of which can be rolled
the isthmus of the thyroid gland;
6◊◊the suprasternal notch.
Note that the lower border of the cricoid is an important level in the
neck; it corresponds not only to the level of the 6th cervical vertebra but
also to:
1◊◊the junction of the larynx with the trachea;
2◊◊the junction of the pharynx with the oesophagus;
3◊◊the level at which the inferior thyroid artery and the middle thyroid
vein enter the thyroid gland;
4◊◊the level at which the vertebral artery enters the transverse foramen in
the 6th cervical vertebra;
5◊◊the level at which the superior belly of the omohyoid crosses the carotid
sheath;
6◊◊the level of the middle cervical sympathetic ganglion;
7◊◊the site at which the carotid artery can be compressed against the trans-
verse process of C6 (the carotid tubercle).
By pressing the jaw laterally against the resistance of one’s hand, the
opposite sternocleidomastoid is tensed. This muscle helps define the poste-
rior triangle of the neck, bounded by sternocleidomastoid, trapezius and
the clavicle, and the anterior triangle, defined by sternocleidomastoid, the
mandible and the midline (Fig. 187).
Violently clench the jaws; the platysma then comes into view as a sheet
of muscle, passing from the mandible down over the clavicles, lying in the
superficial fascia of the neck. The external jugular vein lies immediately deep
to platysma, crosses the sternocleidomastoid into the posterior triangle,
perforates the deep fascia just above the clavicle and enters the subclavian
vein. It is readily visible in a thin subject on straining and is seen from the
audience when a singer hits a sustained high note or when an orthopaedic
surgeon reduces a fracture.
The common carotid artery pulse can be felt by pressing backwards
against the long anterior tubercle of the transverse process of C6. The line
of the carotid sheath can be marked out by a line joining a point mid-
way between the tip of the mastoid process and the angle of the jaw to the
sternoclavicular joint. Along this line, the carotid bifurcates into the external
and internal carotid arteries at the level of the upper border of the thyroid
cartilage; at this level the vessels lie just below the deep fascia where their
pulsation is palpable and often visible.
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